More Instant Messaging Interoperability R. Mahy Internet-Draft Your Organization Here Intended status: Informational 22 April 2025 Expires: 24 October 2025 Conveying the More Instant Messaging Interoperability Message ID in Messaging Layer Security Additional Authenticated Data draft-mahy-mimi-msgid-aad-00 Abstract The More Instant Messaging Interoperability (MIMI) content format defines a MIMI Message ID, communicated only to members of the Messaging Layer Security (MLS) group in which the message was sent. This document defines a way to share a Message ID in the MLS Additional Authenticated Data (AAD) so it is visible to MIMI providers. About This Document This note is to be removed before publishing as an RFC. The latest revision of this draft can be found at https://rohanmahy.github.io/mimi-msgid-aad/draft-mahy-mimi-msgid- aad.html. Status information for this document may be found at https://datatracker.ietf.org/doc/draft-mahy-mimi-msgid-aad/. Discussion of this document takes place on the More Instant Messaging Interoperability mailing list (mailto:mimi@ietf.org), which is archived at https://mailarchive.ietf.org/arch/browse/mimi/. Subscribe at https://www.ietf.org/mailman/listinfo/mimi/. Source for this draft and an issue tracker can be found at https://github.com/rohanmahy/mimi-msgid-aad. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at https://datatracker.ietf.org/drafts/current/. Mahy Expires 24 October 2025 [Page 1] Internet-Draft MIMI Message ID in AAD April 2025 Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on 24 October 2025. Copyright Notice Copyright (c) 2025 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/ license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Revised BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Revised BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Conventions and Definitions . . . . . . . . . . . . . . . . . 3 3. Mechanism . . . . . . . . . . . . . . . . . . . . . . . . . . 3 4. Security Considerations . . . . . . . . . . . . . . . . . . . 3 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 3 5.1. message_id MLS Component Type . . . . . . . . . . . . . . 3 6. Normative References . . . . . . . . . . . . . . . . . . . . 3 Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 4 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction Many messaging protocols and formats have a Message ID. The MIMI content format defines how to calculate a MIMI Message ID Section 3.3 of [I-D.ietf-mimi-content] for an application message. A MIMI Message ID is currently only shared end-to-end encrypted with members of the MLS [RFC9420] group in which the message was sent. This document defines an optional mechanism to share a Message ID in the MLS AAD, so it is visible to intermediary providers. This greatly facilitates debugging and troubleshooting, but causes a modest reduction in privacy. Mahy Expires 24 October 2025 [Page 2] Internet-Draft MIMI Message ID in AAD April 2025 2. Conventions and Definitions The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here. 3. Mechanism This document defines a new Safe AAD message_id component as described in Section 4.9 of [I-D.ietf-mls-extensions]. When the content of an MLS application message is a MIMI content message (media type application/mimi-content), if the message_id component is present inside SafeAAD.aad_items, it MUST contain the MIMI content Message ID calculated as described in Section 3.3 of [I-D.ietf-mimi-content]. To the extent that other application formats or media types have a Message ID, the Message ID for an application message of that type or format MAY be conveyed in this extension. 4. Security Considerations An attacker with access to a fragment of message history, and the message logs of a MIMI provider in the path of a message could potentially learn more about the participants of a particular MIMI room or the room's corresponding MLS group. 5. IANA Considerations 5.1. message_id MLS Component Type This document registers a new MLS Component Type in the Specification Required range with the following template: * Value: TBD (new assignment by IANA) * Name: message_id * Where: AD * Recommended: Y * Reference: RFC XXXX 6. Normative References Mahy Expires 24 October 2025 [Page 3] Internet-Draft MIMI Message ID in AAD April 2025 [I-D.ietf-mimi-content] Mahy, R., "More Instant Messaging Interoperability (MIMI) message content", Work in Progress, Internet-Draft, draft- ietf-mimi-content-06, 28 February 2025, . [I-D.ietf-mls-extensions] Robert, R., "The Messaging Layer Security (MLS) Extensions", Work in Progress, Internet-Draft, draft-ietf- mls-extensions-06, 19 February 2025, . [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . [RFC9420] Barnes, R., Beurdouche, B., Robert, R., Millican, J., Omara, E., and K. Cohn-Gordon, "The Messaging Layer Security (MLS) Protocol", RFC 9420, DOI 10.17487/RFC9420, July 2023, . Acknowledgments TODO acknowledge. Author's Address Rohan Mahy Your Organization Here Email: rohan.mahy@gmail.com Mahy Expires 24 October 2025 [Page 4]